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122 lines
3.4 KiB
122 lines
3.4 KiB
const { end_of_stream } = require('../utils');
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const { label_to_encoding } = require('../table');
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class Stream {
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/**
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* A stream represents an ordered sequence of tokens.
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* @param {!(Array.<number>|Uint8Array)} tokens Array of tokens that provide
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* the stream.
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*/
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constructor(tokens) {
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this.tokens = [...tokens]
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// Reversed as push/pop is more efficient than shift/unshift.
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this.tokens.reverse()
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}
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/**
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* @returns True if end-of-stream has been hit.
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*/
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endOfStream() {
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return !this.tokens.length
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}
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/**
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* When a token is read from a stream, the first token in the
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* stream must be returned and subsequently removed, and
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* end-of-stream must be returned otherwise.
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*
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* @return Get the next token from the stream, or end_of_stream.
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*/
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read() {
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if (!this.tokens.length)
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return end_of_stream
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return this.tokens.pop()
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}
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/**
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* When one or more tokens are prepended to a stream, those tokens
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* must be inserted, in given order, before the first token in the
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* stream.
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*
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* @param {(number|!Array.<number>)} token The token(s) to prepend to the
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* stream.
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*/
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prepend(token) {
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if (Array.isArray(token)) {
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var tokens = /**@type {!Array.<number>}*/(token)
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while (tokens.length)
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this.tokens.push(tokens.pop())
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} else {
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this.tokens.push(token)
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}
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}
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/**
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* When one or more tokens are pushed to a stream, those tokens
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* must be inserted, in given order, after the last token in the
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* stream.
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*
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* @param {(number|!Array.<number>)} token The tokens(s) to push to the
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* stream.
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*/
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push(token) {
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if (Array.isArray(token)) {
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const tokens = /**@type {!Array.<number>}*/(token)
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while (tokens.length)
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this.tokens.unshift(tokens.shift())
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} else {
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this.tokens.unshift(token)
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}
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}
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}
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const DEFAULT_ENCODING = 'utf-8'
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/**
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* Returns the encoding for the label.
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* @param {string} label The encoding label.
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*/
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function getEncoding(label) {
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// 1. Remove any leading and trailing ASCII whitespace from label.
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label = String(label).trim().toLowerCase()
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// 2. If label is an ASCII case-insensitive match for any of the
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// labels listed in the table below, return the corresponding
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// encoding, and failure otherwise.
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if (Object.prototype.hasOwnProperty.call(label_to_encoding, label)) {
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return label_to_encoding[label]
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}
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return null
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}
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//
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// 5. Encodings
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//
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// 5.1 Encoders and decoders
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// /** @interface */
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// function Decoder() {}
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// Decoder.prototype = {
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// /**
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// * @param {Stream} stream The stream of bytes being decoded.
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// * @param {number} bite The next byte read from the stream.
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// * @return {?(number|!Array.<number>)} The next code point(s)
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// * decoded, or null if not enough data exists in the input
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// * stream to decode a complete code point, or |finished|.
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// */
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// handler: function(stream, bite) {},
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// }
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// /** @interface */
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// function Encoder() {}
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// Encoder.prototype = {
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// /**
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// * @param {Stream} stream The stream of code points being encoded.
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// * @param {number} code_point Next code point read from the stream.
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// * @return {(number|!Array.<number>)} Byte(s) to emit, or |finished|.
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// */
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// handler: function(stream, code_point) {},
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// }
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module.exports = Stream
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module.exports.DEFAULT_ENCODING = DEFAULT_ENCODING
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module.exports.getEncoding = getEncoding |